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Low temperature characteristics of SiPMs after very high neutron irradiation
摘要： The design of the CMS phase II upgrade for the HL-LHC uses SiPMs for the Barrel Timing Layer (BTL) and the Behind HCAL detector (BH or CEH). In both sub-detectors the SiPMs will see a 1 MeV equivalent dose of around 1014 n/cm2. To lower the noise in the SiPMs the design is to keep the SiPMs at a low temperature of ?30 ?C. Different samples from two manufactures of SiPMs were irradiated to a total dose of resp. 2 × 1012, 5 × 1013 at the TRIGA reactor at the JSI in Slovenia. The noise in SiPMs is dominated by trap assisted tunneling which is a result of the high internal electric field in SiPMs. We therefore studied the noise behavior from +10 ?C to ?40 ?C from standard high internal field and specially designed low field SiPMs from FBK-irst and Hamamatsu. After the initial characterization before annealing the noise decrease in SiPMs was also studied using accelerated annealing.
关键词： Silicon photomultiplier,MPPC,CMS,GAPD,Radiation damage
更新于2025-09-23 15:23:52
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Effect of monatomic and molecular ion irradiation on time resolved photoluminescence decay in GaN
摘要： Optical effects induced in silicon-doped wurtzite (0001) GaN epilayers by keV monatomic and molecular ion irradiation were experimentally investigated. Results were analyzed together with data on structure defect formation. In all the cases under consideration, an increase in the collision cascade density (the cases of molecular and heavy atomic ion bombardment) enhances the stable damage accumulation rate and, accordingly, intensifies quenching of luminescence. The processes of PL suppression were theoretically considered as an increase of surface recombination rate of nonequilibrium photo-excited charge carriers due to production of stable damage at the irradiated subsurface layer. It is shown that carrier diffusion determines PL decay time shortening in the shallow implantation cases studied.
关键词： Radiation damage,Photoluminescence,Collision cascade density,Time-resolved PL,Charge carrier diffusion,Ion implantation,GaN
更新于2025-09-23 15:23:52
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Size dependent radiation-stability of ZnO and TiO2 particles
摘要： ZnO and TiO2 particles are typical pigments used in solar reflective coatings. In this letter, the radiation stability of ZnO and TiO2 particles within submicron (several hundred nm) and nanoscale (30 nm) size is systematically studied. We reported previously that the 90 nm and 300 nm ZnO particles have nearly a same radiation tolerance (Phys. Status Solidi B 2017, 254, 1600411). Unexpectedly, we found herein that the 30 nm oxides have significant higher radiation tolerance in relation to the submicron particles. Detailed analysis illustrated that the abundant native defects and surface/interface states in oxides nanocrystals, in-situ restored radiation damage through rapid diffusion and annihilation with implantation created vacancies. This work would be beneficial for developing nanoscaled oxides and devices used for space and nuclear radiative environments.
关键词： radiation damage,optical properties,TiO2,ZnO
更新于2025-09-23 15:22:29
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Single photon detection with SiPMs irradiated up to 1014?cm?2 1-MeV-equivalent neutron fluence
摘要： Silicon photomultipliers (SiPM) are solid state light detectors with sensitivity to single photons. Their use in high energy physics experiments, and in particular in ring imaging Cherenkov (RICH) detectors, is hindered by their poor tolerance to radiation. At room temperature the large increase in dark count rate makes single photon detection practically impossible already at 1011 cm?2 1-MeV-equivalent neutron fluence. The neutron fluences foreseen by many subdetectors to be operated at the high luminosity LHC range up to 1014 cm?2 1-MeV-equivalent. In this paper we present the effects of such high neutron fluences on Hamamatsu and SensL SiPMs of different cell size. The advantage of annealing at high temperature (up to 175?C) is discussed. We demonstrate that, after annealing, operation at the single photon level with a SiPM irradiated up to 1014 cm?2 1-MeV-equivalent neutron fluence is possible at cryogenic temperature (77 K) with a dark count rate below 1 kHz.
关键词： Cryogenic temperature,Radiation damage,Single photon detection,SiPM,Neutron irradiation,Annealing
更新于2025-09-23 15:22:29
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Handbook of Materials Modeling (Applications: Current and Emerging Materials) || Incorporating Electronic Effects in Molecular Dynamics Simulations of Neutron and Ion-Induced Collision Cascades
摘要： Molecular dynamics offers an ideal method for investigating the evolution of collision cascades and the formation of the resulting primary radiation damage. However, several modifications to classical molecular dynamics are needed in order to facilitate simulating the highly non-equilibrium cascade process. One such modification, which is still a point of active research, concerns methods by which electronic effects, which are expected to be important in collision cascades, can be included in molecular dynamics simulations, where a priori atoms are treated as classical particles and electrons are only present implicitly through the atomic interactions represented by the interatomic potential. This chapter describes current methods by which electronic effects can be accounted for in cascade simulations, with special focus on the developments in the field that have taken place over the last 10 years.
关键词： interatomic potential,collision cascades,electronic effects,radiation damage,Molecular dynamics
更新于2025-09-23 15:21:21
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Structural dynamics in proteins induced by and probed with X-ray free-electron laser pulses
摘要： X-ray free-electron lasers (XFELs) enable crystallographic structure determination beyond the limitations imposed upon synchrotron measurements by radiation damage. The need for very short XFEL pulses is relieved through gating of Bragg diffraction by loss of crystalline order as damage progresses, but not if ionization events are spatially non-uniform due to underlying elemental distributions, as in biological samples. Indeed, correlated movements of iron and sulfur ions were observed in XFEL-irradiated ferredoxin microcrystals using unusually long pulses of 80 fs. Here, we report a femtosecond time-resolved X-ray pump/X-ray probe experiment on protein nanocrystals. We observe changes in the protein backbone and aromatic residues as well as disulfide bridges. Simulations show that the latter’s correlated structural dynamics are much slower than expected for the predicted high atomic charge states due to significant impact of ion caging and plasma electron screening. This indicates that dense-environment effects can strongly affect local radiation damage-induced structural dynamics.
关键词： plasma electron screening,radiation damage,ion caging,structural dynamics,protein nanocrystals,X-ray free-electron lasers
更新于2025-09-23 15:21:01
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reveals remarkable optical linewidths and fine structure for well-known damage centers
摘要： Luminescence and optical absorption due to radiation damage centers in silicon have been studied exhaustively for decades, but are receiving new interest for applications as emitters for integrated silicon photonic technologies. While a variety of other optical transitions have been found to be much sharper in enriched 28Si than in natural Si, due to the elimination of inhomogeneous isotopic broadening, this has not yet been investigated for radiation damage centers. We report results for the well-known G, W, and C damage centers in highly enriched 28Si, with optical linewidth improvements in some cases of over two orders of magnitude, revealing previously hidden ?ne structure in the G-center emission and absorption. These results have direct implications for the linewidths to be expected from single-center emission, even in natural Si, and for models for the G-center structure. The advantages of 28Si can be readily extended to the study of other radiation damage centers in Si.
关键词： 28Si,silicon,fine structure,optical linewidths,radiation damage centers
更新于2025-09-23 15:21:01
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Study of radiation damage and possible upgrade of the CMS ECAL Laser Monitoring system
摘要： The Electromagnetic Calorimeter (ECAL), one of the main subsystems of the CMS detector, measures the energies of electrons and photons. The ECAL consists of 75848 lead tungstate (PbWO4) crystals. The transparency of crystals is affected by irradiation, and the laser monitoring system is designed to measure the transparency changes for each ECAL crystal over time. In the future, the High-Luminosity LHC upgrade will increase the integrated luminosuty of the LHC and lead to higher radiation damage in all components of the CMS detector. In this work we report the proposed upgrade for the laser monitoring system and the results of computing crystal transparencies based on Run 2 data.
关键词： Laser Monitoring system,radiation damage,crystal transparency,High-Luminosity LHC,CMS ECAL
更新于2025-09-23 15:19:57
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In-Line Holography in Transmission Electron Microscopy for the Atomic Resolution Imaging of Single Particle of Radiation-Sensitive Matter
摘要： In this paper, for the first time it is shown how in-line holography in Transmission Electron Microscopy (TEM) enables the study of radiation-sensitive nanoparticles of organic and inorganic materials providing high-contrast holograms of single nanoparticles, while illuminating specimens with a density of current as low as 1–2 e???2s?1. This provides a powerful method for true single-particle atomic resolution imaging and opens up new perspectives for the study of soft matter in biology and materials science. The approach is not limited to a particular class of TEM specimens, such as homogenous samples or samples specially designed for a particular TEM experiment, but has better application in the study of those specimens with differences in shape, chemical composition, crystallography, and orientation, which cannot be currently addressed at atomic resolution.
关键词： TEM,radiation damage,atomic resolution imaging,nanostructured drugs,organic materials,in-line holography,soft matter,single particle imaging
更新于2025-09-23 15:19:57
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Irradiation and dosimetry arrangement for a radiobiological experiment employing laser-accelerated protons
摘要： The Bragg Peak is a unique characteristic of ion beams which makes their use beneficial in cancer treatment as it allows the majority of dose deposition to be localised in a precise volume. The use of a laser system for particle acceleration is currently investigated as a potential alternative to the conventional RF accelerators currently used for hadrontherapy. The biological response of cells irradiated by high dose-rate laser-driven ions is currently being explored in this context. The experiment reported here was carried out as part of the A-SAIL project, a UK-wide collaboration aiming to develop innovative techniques for accelerating ions for future clinical applications. In this contest, a radiobiological experiment was carried out on the pico2000 laser beamline at LULI-école Polytechnique using an energetically spread, laser-accelerated proton beam. This paper will discuss the arrangement used in the experiment, and the techniques employed for an accurate estimation of the dose deposited, supported by Monte Carlo simulations of the particle propagation through the irradiation system.
关键词： Ion sources,Lasers,Radiation damage evaluation methods
更新于2025-09-12 10:27:22